Yours is first and foremost a theoretical argument. The authors of the Refactoring Browser and I understand these theoretical concerns (about not having static type safety). However, there is theory and there is practice. The two are not identical, and practice trumps theory (see also: science). And in practice, that theoretical concern appears to not have been an issue.
You also argue with hypotheticals (may...depend, likely be the case etc.). Why is that so? Is it because you can't accept that reality doesn't conform to your theory?
Once again: the argument was "you can't". That is as patently false as can be, in reality is it not just "you most definitely can", but "this system is extremely well suited for building this type of tool and in fact the whole category was invented on that system".
And your theoretical concerns notwithstanding, people who have actually used the system consider it best-of-breed.
A scientific approach adapts theory to observation. Theology adapts observation to theory.